This invention relates to wire matrix point head apparatus of the general type disclosed in prior U.S. Pat. Nos. 3,929,214 and 3,994,381.
In general, this invention comprises an improvement in a wire matrix print head assembly and apparatus disclosed in my co-pending U.S. application Ser. No. 809,423, filed June 23, 1977, the disclosure of which is hereby incorporated herein by reference.
In prior art apparatus, such as that disclosed in the afore-identified United States patents and application, wire type printing members (stylus or styli) are arranged in spaced relationship about a central longitudinal axis in a generally circular or elliptical matrix for reciprocable movement between a non-print position and a print position with the movement from the non-print position to the print position being of ballistic nature, i.e. by impact and/or driving engagement with another moving member. Each printing member is operatively associated with a radially innermost portion of a radially outwardly extending armature member and ballistically driven thereby by impact therewith during pivotal movement of the armature from a non-print position to a print position. A radially outermost portion of each armature is operatively associated with a radially outwardly located and circumferentially spaced electromagnetic means having radially spaced pole portions including a radially innermost pole portion and a radially outermost pole portion, the pole portions including flat coplanar radially spaced and radially extending end surfaces which face away from the direction of movement from the non-print position to the print position and engaging a hole surface of the armature at various times. In prior art apparatus, the construction and arrangement has been such that the armature was pivotally supported at all times on a radially outermost edge of the end surface of the radially outermost pole portion and impacted the end surface of the radially innermost pole portion which was constructed and arranged to cause pivotal movement of the armature from the non-print position to the print position by magnetic attraction. In addition, the construction and arrangement was such that the armature impacted on the end surface of the innermost pole portion at approximately the same time that the printing member is being driven through the paper. The result was that the kinetic energy of the armature was lost and only the kinetic energy of the printing member was thereafter effective to cause completion of the printing operation. In fact, of the kinetic energy available just prior to impact of the armature with the surface of the pole portion, approximately two-thirds was lost through armature impact with only approximately one-third remaining in the printing member to accomplish the printing operation. The lost two-thirds of the available kinetic energy was simply dissipated upon impact with the surface of the pole portion with resultant high levels of noise and heat. In addition, the speed of the printing process was reduced and the number of sheets of paper which could be printed at one time was also limited. Furthermore, in order to obtain sufficiently high levels of kinetic energy to produce satisfactory printing results, relatively high levels of energy were required to operate the electromagnetic means.
In the invention of my prior application, the armature members and the electromagnetic means were constructed and arranged so that the armature members were normally pivotally supported by a first pivot means on a radially innermost edge of a radially innermost pole portion while being magnetically attracted by a radially outermost pole portion. In addition, the pole portions were constructed and arranged so that the end surfaces thereof faced toward the direction of movement of the armature and the printing members from the non-print position to the print position. As a result, the driving movement of the armature continued after impact with the end surface of the outermost pole portion without loss of a substantial portion of the kinetic energy thereof as in prior art apparatus. Furthermore, the construction and arrangement was such that after impact of the armature with the end surface of the outermost pole portion, the first pivot means was disengaged and a second pivotal means was provided between a radially outermost portion of the armature and the radially outermost edge of the radially outermost pole portion whereby the driving movement of the armature could continue substantially unimpeded until completion of the printing operation. The prior invention further provided for new and improved mounting of the apparatus including the use of housing means made of one piece of molded plastic material which mounted and supported all of the apparatus in a new and improved manner. The electromagnetic means comprised a one piece member of sintered powder metallic material providing an end plate having the pole portions integral therewith. Also, the one piece electromagnet member was mounted on the one piece housing means in a manner requiring only one threaded fastening means which could be readily adjusted to vary the axial air gap between the end surfaces of the pole portions and the armature as well as adjusting the armature movement.
The present invention involves improvements in the manner of mounting and supporting the armature members. In general, the invention comprises a construction and arrangement wherein radially intermediate portions of the armature members are pivotally supported on the radially innermost magnetic pole portions with a resilient O-ring member located opposite thereto and continuously engaging each armature member. Each of the radially innermost pole portions are positively uniformly located and positioned relative to the O-ring member by abutting engagement with the portion of the armature housing supporting the O-ring member. The radially innermost portions of the armature members are engageable with an adjacent continuous annular side surface of a resilient locating ring member in the non-print position. Adjustment and locating means are provided to uniformly axially adjust the location and position of the resilient locating ring member relative to the innermost portions of the armature members to thereby uniformly axially adjust the location and position of each armature member relative to the wire print members, which are driven by the radially innermost end portions of the armature members, and also the location and position of the armature members relative to the inner pole portions.